There are provided mechanisms for establishing a cooperating cluster (6a) in a cellular communications system (la-Id). According to one aspect a request for establishing a cooperating cluster (6a) to a second network node (2b) is transmitted from a first network node (2a). The cooperating cluster (6a) comprises at least one cell (3b, 3f) of the first network node (2a) and at least one cell (3g) of the second network node (2b). The request comprises a metric and identification of the cells to be clustered. An acceptance is by the first network node (2a) received (S104) from the second network node (2b) to implement operation of the cooperating cluster (6a).